Well cleaning with mixed liquefied propane and butane solvent



Nov. 11-, 1969 J. o; FERGUSON 3,477,513

WELL CLEANING WITH MIXED LIQUEFIED PROPANE AND BUTANE SOLVENT Filed May a, 1968 saw/m wk PUMP 0/?! Vf Jc'vm e.) .0. Feryu: oh

INVENTOR.

ATTORNEY fU. s.- c1, 166- 304 Uniwd St 3,477,513- a I WITH MIXED LIQUEFIED ,PROPANE AND BUYTANEISOLVENT llanies' D.'Eerguson, .letferson County, Tex., assignor to Petro Well Service, Inc., Winnie, Tex., a corporation of Texas v Filed May 8,1968, Ser. No. 727,592

Int. 'Cl. E21b 21/00 8 Claims fkiasTRACT oFTHE DISCLOSURE The invention disclosed is a method for cleaning wells,

primarily pumping wellsQwith specific mixtures of the liquefied 'p'etroleumgases, propane and butane, to removeparaflin and parafiin-sand mixtures, or the like,

from the wells.

' BACKGROUND OF THE INVENTION Field of the invention tions, tubings, casings, and the like, with solvents.

SUMMARY OF THE INVENTION The method for cleaning wells according to the invention involves forced (pumped) introduction of a solvent mixture down a well annulus to the bottom of the well, where the solvent mixture enters the formation, enters the production tubing, and admixes with the liquid petroleum of the formation. The solvent mixture, which consists of a specific mixture of liquefied propane and butane, dissolves paraflin, paraffin-sand mixtures, and like solid or near solid materials, from the formation and equipment in the well, while the well remains in production, with the pump continued in operation in the case of a well from which production is obtained by pumping, or with production flow uninterrupted in the case of a non-pumping well. It is possible to utilize the invention as well with interruption of production, by pressured introduction of the solvent mixture to displace other fluids from the well zone to be cleaned, e.g. drilling muds, liquid petroleum materials, water, gas, etc. The solvent mixture may be introduced through any flow route afforded as dictated by the equipment in place in the well.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic representation showing a petroleum well in vertical cross section and accessory equipment connected therewith suitable for performance of a preferred embodiment of a method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, a well 10 has a casing 11 extending downward from the earths surface 12 to extend through an oil-bearing formation 14. A production pipe string 15 through casing 11 has therein a pump rod 16 extending down to a pump 18 carried at the lower end of string 15. Rod 16 is reciprocated upwardly and downward by a pump drive to cause pumping of liquid petroleum to the surface through tubing 15, the liquid petroleum entering the pump through pump perforations 20.

The showing of the well and equipment is simplified, and the invention may be employed on any well of whatever form equipped in any suitable manner.

Casing 11 is equipped at the well head with a flow passage 22 flow to or from the casing-tubing annulus atent through which is controlled by a wing valve 23. To the wing valve there are connected in series a high pressure check valve 24, a reducer 25, a low pressure checkvalve 26, and a conduit 28 leading from a tank '30 of tank vehicle 31. Other control valves may be-used. All or part of this how connection may be included in the normal equipment of the tank truck, trailer, or the like. A nonvehicle mounted tank or supply may be used.

An outlet 42 at the upper "end of tubing 15 is connected to a conduit 43 leading to a separator 44. Y

A supply of mixed liquefied butane and propane is provided in tank 30. It has been found that a' more or less specific volume ratio of propanerbutane results in very exceptional and superior cleaning of the wells, the volume ratio foroptimum results being, propane:butane=60:40. A relatively small departure from this ratio will result in fairly good well cleaning, but not so good as closer to the optimum ratio. For example, the ratios,"pronpane: butane=70:30 or 50:50 will clean the well only fairly well, and the ratios, propanezbutane=65z35 or 55:45 will perform considerably better, but still below the optimum cleaning resulting from use of the optimal 60:40 ratio.

Of the liquefied gases, propane enhances penetration of the butane, which is of higher dissolving power, and maintains pressure at the area to be cleaned because of its higher vapor pressure. Butane, with its higher dissolving power, dissolves materials more quickly and thoroughly, so that optimum cleaning results. But, surprisingly, the butane and propane must be present in the proper mixture or the extremely efiicient and thorough cleaning of paraflin, paraflin-sand, or the like does not result. The efficiency peaks rapidly, as the optimum volume ratio is approached from either side.

The liquefied propane-butane mixture is delivered (under pump pressure, or equivalent) from tank 30 through conduit 28, through check valves 26 and 24, through open wing valve 23 to the annulus between casing 11 and tubing 15, and down therethrough to the bottom of the well. The pressure against which the propane-butane mixture is pumped must be overcome, either by the pump with which vehicle 31 is equipped, or by other suitable pump, not shown. In the area of Chambers County and Jefferson County, Tex., many pumping wells occur having pressures at the annulus of the order of 40 p.s.i.g., but somewhat lower pressures and much higher pressures occur Where the invention may be employed. The pump must, in all cases, overcome the back pressure in order that the mixture may be introduced effectively.

The propane-butane mixture is preferably introduced without shutting down the well. The down-hole well pump remains in operation throughout, with well production continued. Similarly, with non-pumping wells, production continues during cleaning by the method afforded by the invention. Although the propane-butane mixture is preferably introduced without shutting down the Well, the invention may of course be used while the well is shut down or flow is temporarily interrupted, by forcing the solvent mixture into the well to the paraffin area to be cleaned, through any flow paths present through the equipment in place in the well and displacing any fluids present in the well. These procedures may be used Whether the well is a pumping or a non-pumping well. Pipelines and other equipment are also cleaned by the solvent mixture.

In a trial of the invention in Chambers County, Tex., a 4500 foot well, having an annulus pressure of 42 p.s.i.g. at the wellhead was cleaned by introducing by pumping 500 gallons of propane-butane, ratio 60:40 by volume, during a 15 minute period, to the bottom of the well in the described manner, with the well pump in continuous operation and with continued production. The mixture penetrated into the formation, and admixed with the cleaning resulting from use of the optimum ratio, and

approached optimum cleaning as the optimum ratio was approached.

Another surprising advantage of the invention is that the cleaning lasts up to twice as long, or even longer, than.when cleaning is accomplished by other methods. Also, the cleaning may be completed in a very short time, usually in minutes or less, and certainly not exceeding minutes in most cases.

The solvent mixture, of course, ultimately passes from the well through theproduction tubing with the oil produced, and is separated from the production at separator 44.

While preferred embodiments of the invention have been described and shown, many modifications thereof may be made by a person skilled in the art without departing from the spirit of the invention, and it is intended to protect by Letters Patent all forms of the invention falling within the scope of the following claims.

What is claimed is:

1. Method for cleaning oil wells comprising introducing a mixture of liquefied propane and butane into the well to adjacent the well area to be cleaned to dissolve heavy hydrocarbons including paraflin from the well, said mixture being introduced at a pressure sufiicient to overcome the well pressure, and removing said mixture from the well with the dissolved materials cleaned from the well, said mixture consisting of mixed liquefied propane and butane in a ratio, propane:butane=70:30 to :50, by volume.

2. Method according to claim 1, said ratio, propane: butane=:40, by volume. 1

3. Method according to claim 1, the well being a pumping well.

4. Method according to claim 1, the well being a nonpumping well.

5. Method according to claim 1, said mixture being pressured for introduction as described 'by pumping.

6. Method according to claim 5, said mixture being pumped into the well first through a lowpressure check valve and then through a high pressure check valve, whereby escape from the well of said mixture is prevented and hazardous conditions are not created at thewell.

7. Method according to claim 1, the well-having at least two flow paths therethrough between a petroleumbearing formation and the surface, one of said how paths serving to conduct petroleum from the-formation to the surface, said mixture being introduced into the well through the other of said flow paths and returned to surface admixed with petroleum from the formation through said one of said flow paths.

8. Method for dissolving parafiin for removal thereof. comprising contacting the paraffin with a liquefied solvent mixture of propane and butane wherein the propane: butane ratio (by volume) is from about :30 to about 50:50 for a time sufficient to dissolve the paraflin, and withdrawing the solvent mixture while maintaining the solvent mixture liquefied to remove the paraffin therewith.

References Cited UNITED STATES PATENTS 1,382,337 6/1921 Bellis.

1,484,601 2/1924 Carmichael 166-44 2,699,832 1/1955 Allen l6644 X 2,967,121 1/1961 Allen et a1 166-44 X 2,998,066 8/1961 NiXOn 166-4l 5 CHARLES E. OCONNELL, Primary Examiner IAN A. CALVERT, Assistant Examiner US. Cl. X.R. 2528.55 

